fix(web): admin des bibliothèques — UX, gestion d'erreur, styles

- web: AdminPage (admin bibliothèques), client API, styles
- web: nginx

Refs: #15

apps/web/nginx/default.conf

@@ -26,6 +26,9 @@ server {
   }
 
   location ^~ /admin {
+    if ($http_accept ~* "text/html") {
+      rewrite ^ /index.html last;
+    }
     proxy_pass http://api:3000;
     proxy_set_header Host $host;
     proxy_set_header X-Real-IP $remote_addr;